Mobile Security Deployments (MSD) is a small specialized tactical unit within the Diplomatic Security Service (DSS) of the United States Department of State. The MSD provides U.S. embassies and consulates with security support, protects the secretary of state and other U.S. officials, including domestically as well as visiting foreign officials, and also provides security training at U.S embassies and consulates.

The majority of its operations are overseas with only ten percent conducted in the United States. The unit was formed in 1985 and c. 2002 was renamed Mobile Security Deployments from Mobile Security Division.

MSD is composed of specially trained special agents that typically operate in high-threat environments with little outside support.

Their assignment is the protection of members of the U.S. federal government overseas, particularly at U.S. embassies and consulates. Fighting kidnapping and terrorism are part of their duties, as well as protection and evacuation of U.S. citizens out of crisis areas and training of personnel in foreign countries.

MSD also augments other DSS agents in high-threat or high-profile protection missions.

MSD is based in Dunn Loring, Virginia and consists of a headquarters element, tactical medical staff, training cadre, logistic staff, and thirteen operational teams with six agents each.

The team's three primary missions are:

MSD cooperates closely with other federal agencies, such as the Secret Service, the Fleet Antiterrorism Security Teams of the United States Marine Corps, the Federal Bureau of Investigation and local law enforcement agencies, both domestic and foreign.